1. Field of the Invention
The present invention relates to a touch panel where panels having a conductive thin film provided on a film base are used as upper and lower substrates.
2. Description of the Related Art
Touch panels where bases on which transparent conductive thin films are provided are placed so as to face each other with spacers therebetween are used in such a manner that the above described conductive thin films are used as transparent electrodes. Though conventionally, so-called conductive glass where an indium oxide thin film is formed on a glass as well known for conductive thin films as that described above, it is inferior in terms of flexibility and processability, because the base is a glass, and therefore, it cannot be used for some applications.
Therefore, in recent years, conductive thin films where a variety of plastic films, including polyethylene terephthalate films, are used as the base have been used, because of the benefit in terms of excellent resistance to impact and light weight, in addition to flexibility and processability.
As for conductive thin films where such a film base is used, when input is repeated with a pen or an excessive load is applied by pressing the tip of a pen against the touch panel, the transparent electrode made of a conductive thin film deteriorates or is damaged. In addition, a problem arises, such that the resistance value increases in portions which deteriorate or are damaged, making the life of the touch panel short. That is to say, the conductive thin films make contact with each other when strong pressure is applied at a point from the side of one panel, and therefore, it is desirable for touch panels to have good resistance to this pressure, that is to say, such properties that they are resistant against pressure at localized points, particularly input with a pen.
Thus, attempts have been made to improve film bases on which conductive thin films are provided and which are used in panels, in order to solve the above described problems with touch panels. The present applicant has proposed that a transparent conductive multilayer body where a transparent first dielectric thin film, a transparent second dielectric thin film and a transparent conductive thin film is laminated in this order on one side of a transparent film base, and a transparent base is laminated on the other surface of the above described film base with a transparent pressure-sensitive adhesive layer therebetween be used as a touch panel (see JP-A No. 2002-316378 (pages 2 to 4) and JP-A No. 2002-326301 (pages 2 to 5)). Though touch panels using the transparent conductive multilayer body as that described above have good durability, better durability has been required for touch panels together with the expansion in the market of touch panels.